The trap that is credited as the first patented lethal mousetrap was a set of spring-loaded, cast-iron jaws dubbed "Royal No. 1". It was patented on November 4, 1879, by James M. Keep of New York. From the patent description, it is clear that this is not the first mousetrap of this type, but the patent is for this simplified, easy-to-manufacture, design. It is the industrial age development of the deadfall trap, but relying on the force of a wound spring rather than gravity.